Calcium, the body’s most abundant mineral, plays a critical role in bone health, but it does much more than that. Calcium permits cells to divide, regulates muscle contraction and relaxation, keeps the heart beating and the brain working, plays an important role in the movement of protein and nutrients inside cells, helps control blood pressure, and is essential for blood clotting. Calcium also seems to protect against heart attacks and certain types of cancers.
“We evolved from the ocean, and the ocean is a high-calcium bath,” says Michael Holick, M.D., Ph.D., professor of medicine, dermatology, and physiology at Boston University Medical Center. “Living organisms used calcium for all types of purposes because it was readily available. But now that we’re on land, the lack of calcium in our environment poses a serious risk.”
The body maintains its blood calcium level at any expense, Holick says. So if you’re not absorbing enough calcium from what you eat to satisfy your body’s requirement, you’ll steal it from your bones.
In effect, the body uses its bones as a calcium bank. “It constantly takes calcium from the bone and supplies it to the blood to make sure that all of these essential functions can continue,” explains Bernard P. Halloran, Ph.D., professor of medicine at the University of California San Francisco.
When you eat a piece of cheese, drink a glass of milk, or take a calcium supplement, the calcium is digested in the intestine, where vitamin D stimulates its absorption. It then travels through the body in your blood, where it. s constantly deposited and withdrawn from bone. “It’s as if we put a thousand dollars worth of calcium into the bone each day and remove a thousand dollars worth each day,” says Halloran. “The bone stays in a steady state, but a amount of calcium goes in and out of it.” This ensures that the body always has a source of calcium when it needs it.
You’re Never Too Old
Many adults shrug off the need for adequate calcium and feel it’s not necessary since they’re no longer building bone, a process that ends at about age 30. “But if you continue to consume an inadequate amount of calcium, you’ll gradually erode your skeleton to the point where, one morning, you’ll break a bone when you get out of bed,” warns Halloran.
According to one researcher, if adults simply added one more glass of milk and a cup of yogurt a day, and either walked or participated in some other form of weight-bearing exercise for 30 minutes a day, they could substantially reduce the incidence of broken bones resulting from osteoporosis.
Because vitamin D plays a role in the body’s absorption of calcium, consuming a sufficient amount is also crucially important and simple. Milk has been fortified with vitamin D, so if you drink milk you’re getting enough. And, since your body makes vitamin D when exposed to the sun’s rays, 15 to 30 minutes of sunlight on your face and hands two to three times a week will take care of it. If you don’t drink milk and the weather is gloomy, take a multivitamin that includes vitamin D. But never use supplements of this single vitamin unless your doctor recommends them; too much vitamin D can be toxic.
Good Sources of Calcium
Although the optimal amount of calcium isn’t known, “enough” according to the Food and Nutrition Board of the National Academy of Sciences. Institute of Medicine, is 1,200 milligrams (mg) a day for adults over 50. The most readily available form of calcium is in dairy products.
But you can get calcium from many other foods as well. Tofu, if prepared with calcium sulfate, is an outstanding source. Just one-quarter of a block gives you a substantial 553 mg. Don’t like tofu? Try whizzing it in a blender with some milk or juice, fresh fruit, and a bit of honey to make a nourishing and delicious smoothie. Leafy green vegetables, calcium-fortified fruit juices, canned sardines, and canned salmon with bones are all good sources. Even carrots and green peas contain calcium. To up your consumption of calcium in a way you won’t even notice, add dry milk to soups or sauces. Just one-quarter cup of dry milk provides 375 mg of calcium.
“Milk is a poor source.” Some people believe that drinking milk is not a good way to get calcium because the protein in it carries away the calcium in urine. “Here’s the story,” says Holick. “The body metabolizes the sulfur amino acids in protein and releases sulfuric acid. And that acid, which is excreted in urine, takes calcium along with it.” So it does have a marginal effect on bones. However, if you get enough calcium in your diet, you can more than offset any loss.
“Coffee saps calcium.” A while back, reports warned that drinking caffeinated coffee would leach calcium from bones. “But a nicely done study shows that the amount of calcium in the milk you put into your coffee is enough to make up for the minuscule amount of calcium lost,” Holick says.
“Calcium causes kidney stones.” In the past, people whose risk of kidney stones was high were told to limit the amount of calcium they ate because the stones are made from calcium salts. But current thinking has it that calcium from food actually decreases the risk of kidney stones.
The most important message about calcium is also the simplest: Make sure you get an adequate amount. You don’t have to count milligrams with every bite, but learn which foods are rich in calcium and make them a regular part of your diet. And, to guarantee that the calcium you eat becomes available to your body, get sufficient vitamin D, via the sun or in a multivitamin tablet.